Fluid powered diaphragm pumps are known. A typical design sold under the SANDPIPER.RTM. trademark by Warren Rupp, Inc., a unit of IDEX Corporation, of Mansfield, Ohio is shown in FIG. 1. Specifically, the pump 10 includes two chambers 11, 12 which are defined by the diaphragms 13, 14. The diaphragms 13, 14 are connected by a diaphragm rod 15 by way of the diaphragm plate assemblies 16, 17. Pressurized fluid is supplied to the inner diaphragm chambers 18, 19 by way of a main fluid valve 21. The main fluid valve 21 includes a spool 22 that is slidably accommodated in a housing 23. The housing 23 may also be equipped with a sleeve-like structure 24 that accommodates the spool 22. The spool 22 slides back and forth from left to right in the housing 23 and directs pressurized fluid into the inner diaphragm chambers 18, 19 in a reciprocating fashion. The spool 22, or the main fluid valve 21 is shifted by a pilot valve which is not shown in FIG. 1. Typical prior art pilot valves are powered by air bled off of the pressurized fluid supply which drives the pump. This design has been found to be problematic for the following reasons.
Specifically, when the pump 10 is operating at low speeds or with a pressurized fluid supply at a relatively low pressure, the pilot valve can be starved for power as the pump 10 consumes the bulk of the pressurized supply fluid. Accordingly, the pilot valve may not shift properly and, accordingly, will not direct a sufficient amount of pressurized fluid to either opposing end 25, 26 to properly shift the spool 22 of the main fluid valve 21. Therefore, there is a need for an improved fluid diaphragm pump which avoids the problem associated with the shifting of the pilot valve, and consequently the shifting of the main fluid valve, when the pump is operating with a pressurized fluid supply of a reduced pressure.
Two other problems associated with the operation of fluid powered diaphragm pumps are stalling and sticking. Stalling typically occurs when the pump is operated at low speeds or at a low pressure differential. Stalling can also occur when the main fluid valve components are worn thereby allowing internal fluid leakage or by-pass. In any event, the spool 22 of the main fluid valve 21 becomes stuck at a midpoint between the first and second positions, or left and right positions, and the only reliable means for restarting the pump requires the operator to shut off the pressurized fluid supply and restart the pressurized fluid supply. Typically, operators in this field will attempt to restart the pump by banging on the main fluid valve housing with a hammer or other heavy object, which can damage the pump. This solution is also ineffective because the spool of the pilot valve, along with the spool of the main fluid valve, is typically located at a midpoint between the two shifted positions. The location of the spool of the main fluid valve in the mid-point position diverts or blocks off the supply fluid and prevents the pump from reciprocating.
Stalling is normally associated when the discharge fluid is compressible or includes air or vapor which results in a lower pressure head. As the discharge fluid is compressed and decompressed in the diaphragm chambers, the pilot valve is pulsed, rather than positively shifted, eventually resulting in the building up of balanced air pressures on either side of the pilot valve spool as well as the main fluid valve spool, causing both spools to obtain a centered position in their respective housings. Stalling can also occur with low flow and low speed applications such as the employment of a diaphragm pump in a filter press or in connection with an on-demand spray service. Both applications have low speed and low flow coupled with a low head or dead head. Both applications can also create air or vapor build-up on the discharge side of the pump.
As a result, there is a need for an improved fluid powered diaphragm pump which results in a positive shift of both the pilot valve spool and main fluid valve spool in low speed, low pressure applications.
A pump is considered to be sticking when it fails to restart or stops in the middle of a stroke. Typically, the main fluid valve spool is seized or stuck in the sleeve or housing. This situation occurs most frequently when the pressurized fluid is contaminated or is of a poor quality. Sticking frequently occurs when diaphragm pumps are employed in mines and the pressurized fluid is a poor quality air supply. Because the main fluid valve spool is typically disposed within a solid sleeve structure that, in turn, is attached to the valve housing, it is very difficult to service the main fluid valves of diaphragm pumps. The entire spool and sleeve must be removed and clean in the event sticking occurs.
Accordingly, there is a need for an improved fluid powered diaphragm pump with a main fluid valve that is easier to disassemble and/or service.
Further, currently available diaphragm pumps typically include inefficient exhaust systems. Exhaust systems are required due to the high noise level associated with these pumps. Further, most diaphragm pumps do not come equipped with a versatile exhaust element, meaning that the pump is equipped with its own exhaust and muffler system or, the pump must be modified if the end users is required to pipe the exhaust away from the pump. Further, many exhaust system designs are difficult to disassemble, and disassembly is required on a relatively frequent basis due to the susceptibility of exhaust systems to freezing.
Further, diaphragm pumps are not easily incorporated into electronic interfaces which monitor the pump frequency. Typically, upgrading an existing pump to be interfaced with electronic manufacturing equipment is time consuming and expensive. Accordingly, there is a need for an improved fluid powered diaphragm pump design which enables the pump to be easily integrated with electronic manufacturing equipment.
Still further, there is a need for an improved fluid powered diaphragm pump which may be easily locked so as to prevent the pump from running accidentally. Currently, the only way to lock out a diaphragm pump is to completely disconnect the pressurized fluid supply.